Method of preparing thin supported films by vacuum deposition

ABSTRACT

A method for preparing thin supported films by vacuum is disclosed. The method results in a substrate with windows. The windows are cutout (etched) areas that are covered by a thin film. The method for creating the substrate with thin film covering requires: masking off one surface of the metal substrate with a maskant; placing the metal substrate under a vacuum; treating the unmasked surface by plasma etching; coating the treated surface with a film while still under vacuum; removing substrate from vacuum; remove the masking; treating the previously masked side with photo resist; exposing the side treated with photo resist to artwork of a desired pattern; exposing the substrate to a suitable solution; chemically etching in areas selectively exposed by the artwork; neutralizing the substrate; and removing the etched parts from the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] (Not Applicable)

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

[0002] (Not Applicable)

BACKGROUND OF THE INVENTION

[0003] The present invention relates generally to milling metal andother suitable substrates and more particularly to a method of preparingthin supported films by vacuum deposition and chemical milling.

[0004] Chemically milling substrates is known in the art. For example,patterns can be chemically etched in metal substrates leaving holes inthe shape of the pattern in the substrate. Many applications, such aslaser beams, semi-conductors and integrated circuits require that theholes in the substrate be covered with a thin film. Prior art systemsuse a two-step process to accomplish this. First, the substrate isetched, resulting in a substrate with one or more holes in thesubstrate. Second, a thin film is attached to one side of the substrateso that the thin film covers the holes. This process is problematic inthat the thin film initially must be supported in some manner and thenattached to the substrate. This process is prone to errors, such asdamaging the film during the transferring and adhering process.

[0005] Therefore, a need exists for a system of producing an etchedsubstrate with a thin film covering without having to transfer the thinfilm to the etched substrate.

BRIEF SUMMARY OF THE INVENTION

[0006] The present invention is directed to a method for preparing thinsupported films by vacuum deposition. The method results in a substratewith a window or windows. The windows are cutout (etched) areas whichare covered by a thin film. The method for creating the substrate withthin film covered areas requires: masking off one surface of thesubstrate with a maskant; placing the substrate under a vacuum; treatingthe unmasked surface by plasma etching to clean and enhance adhesion;coating the treated surface with a film while still under vacuum;removing the substrate from vacuum; removing masking; treating thepreviously masked side with photo resist; exposing the side treated withphoto resist to artwork of a desired pattern; then exposing thesubstrate to a suitable solution; chemically etching in areasselectively exposed by the artwork and then neutralizing the substrate.

[0007] In accordance with other aspects of the invention, the substrateis a metal. The metal may be stainless steel, brass copper, silicon, orother materials that can be chemically milled.

[0008] In accordance with still other aspects of the invention, themaskant can be tape, liquid film, wax, or other types of resists.

[0009] In accordance with yet other aspects of the invention the film isproduced by vapor deposition or plasma arc deposition. Preferably, thefilm is parylene, or one of the many types of clear plastic filmsproduced by low-pressure chemical or vapor deposition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These, as well as other features of the present invention, willbecome more apparent upon reference to the drawings wherein:

[0011]FIG. 1 is an exemplary illustration of a substrate with a thinfilm covering over an etched pattern formed in accordance with thepresent invention; and

[0012]FIG. 2 is a flow diagram illustrating exemplary logic for creatinga substrate with a thin film covering over an etched pattern such as thesubstrate shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is directed to a method of preparing thinsupported films by vacuum deposition and chemical milling. The presentinvention is a one-step process in that the film is adhered to the metalprior to the etching process, thus eliminating the need to transfer thefilm to a pre-etched substrate.

[0014]FIG. 1 illustrates an exemplary substrate 20, which has beenprepared using the method of the present invention. In exemplaryembodiments the substrate is a metal substrate, preferably manufacturedfrom stainless steel. It will be appreciated that other metals may besuitable, for example, brass copper, silicon, or other materials thatcan be chemically milled. The substrate 20 is coated with a thin film,preferably parylene. A pattern 22 is then etched into the substrate 20.The etched portion is removed, leaving windows with the film in theetched portion. An exemplary method for creating the substrate withwindows with film as shown in FIG. 1 is illustrated in FIG. 2 anddescribed below.

[0015]FIG. 2 is a flow diagram illustrating exemplary logic for a methodof preparing thin supported films by vacuum deposition and chemicalmilling in accordance with the present invention. The logic moves from astart block to block 30 where the metal substrate is prepared.

[0016] Preferably, the substrate has a mirrored finish in order thatdefects in the substrate's surface will not be replicated in thefinished film sheet. However, almost any substrate that can bechemically etched is suitable. The preparation of metal substrate 20 isaccomplished by completely masking off one surface of the substrate witha suitable maskant, such as tape, liquid film, wax, or other types ofresists. Next, in block 32, the substrate is placed under vacuum andtreated on the exposed (unmasked) surface by plasma etching in order toimprove adhesion. The plasma etching prepares the surface, therebyincreasing the surface area, which improves adhesion. Preferably, theplasma etching is performed on the area that is going to be coated afterthe side being masked.

[0017] Next, in block 34, the treated surface is coated with therequired film while still under vacuum. Preferably, the film is madefrom parylene. However, the film can be made from any chemically inertplastic material that can be deposited under vacuum (e.g., thoseproduced by vapor deposition or plasma arc deposition). Preferably, thefilms are dielectric, however, dielectric films treated for conductivitymay also be used. After deposition of the film, the substrate is removedfrom the vacuum and the masking is removed. See block 36. Next, in block38, the side that has been masked is treated with photo resist and thenexposed using the artwork that corresponds to the configuration of therequired part. Next, in block 40, the substrate is exposed to a suitablesolution such as acid, ferric chloride, etc. and chemically etched inthe areas selectively exposed by use of the artwork in order to create a“window”. After etching, the etching process is terminated by a suitableneutralizing step. See block 42. Finally, in block 44, the etched partsare removed (e.g., cut, sheared or detached) from the substrate.

[0018] Thus, the product of the process described above is the substratewith a cutout pattern which is covered by a thin film (e.g., parylene).Such a product can be used for various applications. For example, makingwindows of optically suitable films for use in x-ray systems, lasers,etc. The windows (film) can be made very thin, for example having athickness of one micron or less. The product produced by the processused above can be used in systems that have a pressure differentialacross the window. Other applications include pellicles for use inoptical systems as beam splitters and filters, etc.

[0019] Additional modifications and improvements of the presentinvention may also be apparent to those of the ordinary skill in theart. Thus, the particular parts described and illustrated herein areintended to represent only one embodiment of the present invention, andis not intended to serve as limitations of alternative devices withinthe spirit and scope of the invention.

1. A method for preparing a thin supported film on a metal substratehaving two surfaces, the method comprising: a. masking off a firstsurface of the metal substrate with a maskant, leaving a second surfaceof the metal substrate unmasked; b. placing the metal substrate under avacuum; c. treating the second unmasked surface of the metal substrateby plasma etching; d. coating the treated second surface of the metalsubstrate with a film while still under vacuum; e. removing the metalsubstrate from the vacuum; f. removing the maskant; g. treating thepreviously masked second surface of the metal substrate with photoresist; h. exposing the treated second surface of the metal substratewith photo resist to artwork of a desired pattern; i. exposing the metalsubstrate to a suitable solution; j. creating at least one etched partof the metal substrate by chemically etching in areas selectivelyexposed by the artwork; k. neutralizing the metal substrate; and l.removing the at least one etched part of the metal substrate.
 2. Themethod of claim 1, wherein the metal substrate is stainless steel. 3.The method of claim 1, wherein the metal substrate is brass copper. 4.The method of claim 1, wherein the metal substrate is silicon.
 5. Themethod of claim 1, wherein the maskant is tape.
 6. The method of claim1, wherein the maskant is liquid film.
 7. The method of claim 1, whereinthe maskant is resist.
 8. The method of claim 1, wherein the maskant iswax.
 9. The method of claim 1, wherein the thin supported film isproduced by plasma arc deposition.
 10. The method of claim 1, whereinthe thin supported film is produced by vapor deposition.
 11. The methodof claim 1, wherein the thin supported film is parylene.
 12. A thinsupported film on a metal substrate having two surfaces created by amethod comprising: a. masking off a first surface of the metal substratewith a maskant, leaving a second surface of the metal substrateunmasked; b. placing the metal substrate under a vacuum; c. treating thesecond unmasked surface of the metal substrate by plasma etching; d.coating the treated second surface of the metal substrate with a filmwhile still under vacuum; e. removing the metal substrate from vacuum;f. removing the maskant; g. treating the previously masked secondsurface of the metal substrate with photo resist; h. exposing the secondsurface of the metal substrate treated with photo resist to artwork of adesired pattern; i. exposing the metal substrate to a suitable solution;j. creating at least one etched part of the metal substrate bychemically etching in areas selectively exposed by the artwork; k.neutralizing the metal substrate; and l. removing the etched parts fromthe metal substrate.
 13. The thin supported film on the metal substrateof claim 12, wherein the metal substrate is stainless steel.
 14. Thethin supported film on the metal substrate of claim 12, wherein themetal substrate is brass copper.
 15. The thin supported film on themetal substrate of claim 12, wherein the metal substrate is silicon. 16.The thin supported film on the substrate of claim 12, wherein themaskant is tape.
 17. The thin supported film on the substrate of claim12, wherein the maskant is liquid film.
 18. The thin supported film onthe substrate of claim 12, wherein the maskant is resist.
 19. The thinsupported film on the substrate of claim 12, wherein the maskant is wax.20. The thin supported film on the substrate of claim 12, wherein thethin supported film is produced by vapor deposition.
 21. The thinsupported film on the substrate of claim 12, wherein the thin supportedfilm is produced by plasma arc deposition.
 22. The thin supported filmon the substrate of claim 12, wherein the thin supported film isparylene.